[LeetCode] 944. Delete Columns to Make Sorted

- Problem

944. Delete Columns to Make Sorted

You are given an array of n strings strs, all of the same length.

The strings can be arranged such that there is one on each line, making a grid. For example, strs = ["abc", "bce", "cae"] can be arranged as:

abc
bce
cae

You want to delete the columns that are not sorted lexicographically. In the above example (0-indexed), columns 0 ('a', 'b', 'c') and 2 ('c', 'e', 'e') are sorted while column 1 ('b', 'c', 'a') is not, so you would delete column 1.

Return the number of columns that you will delete.

Example 1:

Input: strs = ["cba","daf","ghi"]
Output: 1
Explanation: The grid looks as follows:
  cba
  daf
  ghi
Columns 0 and 2 are sorted, but column 1 is not, so you only need to delete 1 column.

Example 2:

Input: strs = ["a","b"]
Output: 0
Explanation: The grid looks as follows:
  a
  b
Column 0 is the only column and is sorted, so you will not delete any columns.

Example 3:

Input: strs = ["zyx","wvu","tsr"]
Output: 3
Explanation: The grid looks as follows:
  zyx
  wvu
  tsr
All 3 columns are not sorted, so you will delete all 3.

Constraints:

• n == strs.length
• 1 <= n <= 100
• 1 <= strs[i].length <= 1000
• strs[i] consists of lowercase English letters.

---

- 내 풀이 (sort)

class Solution:
    def minDeletionSize(self, strs: List[str]) -> int:
        answer, N = 0, len(strs)
        
        for s in zip(*strs):
            if "".join(s) != "".join(sorted(s)):
                answer += 1

        return answer

• 시간 복잡도: O(N*M*logN)

- 결과

---

- 내 풀이 2

class Solution:
    def minDeletionSize(self, strs: List[str]) -> int:
        answer = 0
        M, N = len(strs[0]), len(strs)
        
        for i in range(M):
            for j in range(N-1):
                if strs[j][i] > strs[j+1][i]:
                    answer += 1
                    break

        return answer

• 시간 복잡도: O(MN)

- 결과